Trading card game Arena 9 deals a strong hand on iPhone

By their nature, trading cards games (TCG) are complicated. These are the sort of experiences people spend hundreds of hours playing and hundreds of dollars to expand their decks.

For that reason, you have to be committed to get over the initial 'What the heck's going on?'

It's an even bigger obstacle for computer-based TCGs, as you don't have the help of other physical players to give you advice. It's just you, the computer artificial intelligence and faceless online players.

Preamble over, that's exactly the sort of situation Humble Gaming and co-developer CDE hopes to overcome with their Arena 9 trading card game for iPhone and iPod touch.

Based around a relatively simple playing system - each of your five character cards has a number (one to nine) on each its four edges: lay down a card with a higher number adjacent to your opponent's on the 3 by 3 grid and that card turns your colour - there's also enough layering for real tactics to emerge.

For example, if by laying down a card, you exactly match the numbers on any two sides of the card you're attacking, you perform a mirror move, gaining the card on the further mirrored edge.

here's also an Add move, which happens when by laying down a card, the sum of each edge of the card being attacked are the same. Again, you additionally win that other card.

Combined with these is the Combo, which means that a card turned in such ways becomes active and can further win enemy cards.

And if that wasn't enough, there's a paper-scissors-stone elemental trumping system (actually there are five elements), enabling you to pull off elemental kills, as well as using buffs and debuffs when the grid contains pre-set elemental positions.

Such opportunities means games are open until the final card is laid, although as you can see your opponent's deck, you can limit their final moves with forethought.

How's this simple, you may be asking?

Well, for one thing, it's the sort of gameplay that harder to explain in words than understand.

Secondly, games are really quick as you only have 30 seconds or so to make your moves, and with a small grid, you quickly get the hang of what's going on.

For another, there's an offline practice mode so you can get to grips with the gameplay without feeling too embarrassed about losing. When you're ready for that, there's the ranking online mode (using OpenFeint), which has the option of playing the server or other human players

Of course, the true value of the game will be seen after many hours of play, but with a typical deck expansion system in terms of gaining new cards - either using real money or the in-game credits you build up by progression - and a fresh, funky art style, it looks like Arena 9 has a good opportunity to lay down its mark on the App Store.

Arena 9 is out now and free to play.